一、数据表结构及实体类(数据表字段与bean属性完全对应)
package com.itheima.domain; import java.io.Serializable; public class Account implements Serializable { private Integer id; private Integer uid; private Double money; //多对一（mybatis中称之为一对一）的映射：一个账户只能属于一个用户 private User user; public User getUser() { return user; } public void setUser(User user) { this.user = user; } public Integer getId() { return id; } public void setId(Integer id) { this.id = id; } public Integer getUid() { return uid; } public void setUid(Integer uid) { this.uid = uid; } public Double getMoney() { return money; } public void setMoney(Double money) { this.money = money; } @Override public String toString() { return "Account{" + "id=" + id + ", uid=" + uid + ", money=" + money + '}'; } }
package com.itheima.domain; import java.io.Serializable; import java.util.Date; import java.util.List; public class User implements Serializable{ private Integer userId; private String userName; private String userAddress; private String userSex; private Date userBirthday; //一对多关系映射：一个用户对应多个账户 private List<Account> accounts; public List<Account> getAccounts() { return accounts; } public void setAccounts(List<Account> accounts) { this.accounts = accounts; } public Integer getUserId() { return userId; } public void setUserId(Integer userId) { this.userId = userId; } public String getUserName() { return userName; } public void setUserName(String userName) { this.userName = userName; } public String getUserAddress() { return userAddress; } public void setUserAddress(String userAddress) { this.userAddress = userAddress; } public String getUserSex() { return userSex; } public void setUserSex(String userSex) { this.userSex = userSex; } public Date getUserBirthday() { return userBirthday; } public void setUserBirthday(Date userBirthday) { this.userBirthday = userBirthday; } @Override public String toString() { return "User{" + "userId=" + userId + ", userName='" + userName + '\'' + ", userAddress='" + userAddress + '\'' + ", userSex='" + userSex + '\'' + ", userBirthday=" + userBirthday + '}'; } }
二、一对一查询
package com.itheima.dao; import com.itheima.domain.Account; import org.apache.ibatis.annotations.One; import org.apache.ibatis.annotations.Result; import org.apache.ibatis.annotations.Results; import org.apache.ibatis.annotations.Select; import org.apache.ibatis.mapping.FetchType; import java.util.List; public interface IAccountDao { /** * 查询所有账户，并且获取每个账户所属的用户信息 * @return */ @Select("select * from account") @Results(id="accountMap",value = { @Result(id=true,column = "id",property = "id"), @Result(column = "uid",property = "uid"), @Result(column = "money",property = "money"), @Result(property = "user",column = "uid",one=@One(select="com.itheima.dao.IUserDao.findById",fetchType= FetchType.EAGER)) }) List<Account> findAll(); /** * 根据用户id查询账户信息 * @param userId * @return */ @Select("select * from account where uid = #{userId}") List<Account> findAccountByUid(Integer userId); }
三、一对多查询
package com.itheima.dao; import com.itheima.domain.User; import org.apache.ibatis.annotations.*; import org.apache.ibatis.mapping.FetchType; import java.util.List; @CacheNamespace(blocking = true) public interface IUserDao { /** * 查询所有用户 * @return */ @Select("select * from user") @Results(id="userMap",value={ @Result(id=true,column = "id",property = "userId"), @Result(column = "username",property = "userName"), @Result(column = "address",property = "userAddress"), @Result(column = "sex",property = "userSex"), @Result(column = "birthday",property = "userBirthday"), @Result(property = "accounts",column = "id", many = @Many(select = "com.itheima.dao.IAccountDao.findAccountByUid", fetchType = FetchType.LAZY)) }) List<User> findAll(); /** * 根据id查询用户 * @param userId * @return */ @Select("select * from user where id=#{id} ") @ResultMap("userMap") User findById(Integer userId); /** * 根据用户名称模糊查询 * @param username * @return */ @Select("select * from user where username like #{username} ") @ResultMap("userMap") List<User> findUserByName(String username); }
